l = range(0,100000)
for i in l:
  if i%1000==0:
    print i
  for j in l:
    s = i + j

screen -d -m -L python test.py

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>


char *getenv(const char *s) {
    static char *(*getenv_real)(const char *s) = NULL;

    if (getenv_real == NULL) {
        getenv_real = dlsym(RTLD_NEXT, "getenv");

        setlinebuf(stdout);
    }

    return getenv_real(s);
}

gcc -O2 -o linebufferedstdout.so -fpic -shared linebufferedstdout.c -ldl -lc

$ LD_PRELOAD=./linebufferedstdout.so python test.py | tee -a test.out
0
1000
2000
3000
4000

./program | tee a.txt

$ sudo apt-get install expect
$ unbuffer python program.py | cat -
<watch output immediately show up here>